Sexual dimorphism in clock genes expression in human adipose tissue

This study was carried out to investigate whether sex-related differences exist in the adipocyte expression of clock genes from subcutaneous abdominal and visceral fat depots in severely obese patients.

We investigated 16 morbidly obese patients, eight men and eight women (mean age 45 ± 20 years; mean BMI 46 ± 6 kg/m(2)), undergoing laparoscopic gastric bypass surgery. Biopsies were taken as paired samples [subcutaneous and visceral adipose tissue (AT)] at the beginning of the surgical process at 11:00 h in the morning. Metabolic syndrome features such as waist circumference, plasma glucose, triglycerides, total cholesterol, high-density lipoprotein cholesterol (HDL-C), and low-density lipoprotein cholesterol (LDL-C) were also studied. The expression of clock genes (PER2, BMAL1, and CRY1) was measured by quantitative real-time PCR, Western blot, and immunohistochemical analysis.

Gene expression was significantly higher in women than in men for the three genes studied in both ATs (P < 0.05). In visceral fat, these differences were more marked. (P < 0.001). Western blot analysis partially confirmed these results since statistical differences were observed for PER2 in both ATs and for CRY1 in subcutaneous adipose tissue. There were no differences in BMAL1 protein expression. Interestingly, clock gene expression level was correlated with LDL-C and HDL-C (P < 0.05). Moreover, we found significant associations with body fat mass in women and with age in men.

Clock genes expression is sex dependent in human adipose tissue from morbidly obese subjects and correlates to a decreased in metabolic syndrome-related traits. These preliminary results make necessary to go deep into the knowledge of the molecular basis of the sexual dimorphism in chronobiology.